ath10k: fix misreported tx bandwidth for 160Mhz

Because of this missing switch case, 160Mhz transmit was reported as
20Mhz, leading to wrong airtime calculation and AQL limiting max
throughput.

Tested-on: QCA9984 hw2.0 PCI 10.4-3.10-00047

Signed-off-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/cd2735a40da7f4fcc5323e3fca3775e7b5402ece.camel@freebox.fr